In the manufacture of a semiconductor device, a method for bonding a semiconductor element to an adherend such as a metal lead frame (a so-called die bonding method) has been developed from a conventional method for using gold-silicon eutectic bonding to a method for using solder or a resin paste. At the present time, an electrically conductive resin paste may be used.
However, there have been problems in the method for using a resin paste such as a decrease in electrical conductivity due to voids, nonuniformity of the thickness of the resin paste, and contamination of a pad due to protrusion of the resin paste. A polyimide resin-containing film adhesive may be used in place of the resin paste in order to solve these problems (for example, see Patent Document 1).
An acrylic resin-containing film adhesive has also been known. For example, a technique of improving flexibility and reducing heat damage of a lead frame or the like using an acrylic acid copolymer having a glass transition temperature of −10° C. to 50° C. is described in Patent Document 2.
On the other hand, in recent years, a power semiconductor device for controlling and supplying electric power has been remarkably widely used. Since a current always flows in the power semiconductor device, the power semiconductor device has a large heating value. Therefore, an electrically conductive adhesive used for the power semiconductor device desirably has high heat dissipation properties and low electric resistivity.
Low loss and a high-speed operation are required for the power semiconductor device. Conventionally, semiconductors using Si such as IGBT (Insulated Gate Bipolar Transistor) and MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) have been used for the power semiconductor device. In recent years, power semiconductor devices using semiconductors such as SiC and GaN have been developed, and are expected to expand from now on.
The semiconductors using SiC and GaN have features such as a large band gap and a high breakdown electrical field to achieve low loss, a high-speed operation, and a high-temperature operation. The high-temperature operation provides a merit in an automobile and a small power converter or the like used in a severe heat environment. In the semiconductor device used in a severe heat environment, a high-temperature operation at about 250° C. is assumed. This causes problems in heat characteristics and reliability in solder and an electrically conductive adhesive as conventional bonding and adhesive materials. Then, conventionally, a sintering metal particle-containing paste material has been proposed (for example, see Patent Document 3). The sintering metal particle-containing paste material contains nanomicro-sized metal particles. These metal particles are melted at a temperature lower than a usual melting point according to a nanosize effect, so that sintering between the particles is achieved. Bonding due to sintering provides high reliability even in an environment of 250° C. and high heat characteristics.